||First research, speciation of arsenic and selenium in human urine was carried out using ion chromatography (IC) for separation and inductively coupled mass spectrometry (ICP-MS) for detection. The arsenic and selenium species studied were arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB) and selenite [Se(IV)], selenate [Se(IV)]. Chromatographic separation of all the species was achieved in <11 min in gradient elution mode using (NH4)2CO3 and methanol at pH 8.8. The outlet of the IC column was directly connected to the nebulizer of ICP-MS for the determination of arsenic and selenium. The speciation of arsenic and selenium have been carried out in human urine samples. The recoveries from spiked samples were in the range of 91−109%. The unknown compounds detected in human urine were identified by coupling IC directly with electrospray ionization−mass spectrometry (ESI-MS). Selenosugar was identified in human urine. The limits of detection were in the range of 0.008−0.015 ng mL−1 for various arsenic species and 0.022-0.030 ng mL−1 for various selenium species based on peak height.|
Second research, a HPLC separation procedure has been developed for the speciation of Cr(III), Cr(VI) and As(III), As(V), DMA, MMA, AsB in dietary supplement samples. The species were separated on anion-exchange LC in gradient elution mode. The mobile phase consisting of EDTA and (NH4)2CO3 at pH 8.8, operated in a linear ramp, yielded well resolved chromatograms of all the species within 14 min with retention times of less than 2% RSD. The analyses were carried out using dynamic reaction cellinductively coupled plasma-mass spectrometer (DRC-ICP-MS). The DRC conditions have also been optimized to obtained interference free measurements of 52Cr, 53Cr and 75As, which were otherwise interfered by: 35Cl16O1H, 40Ar12C on 52Cr; 37Cl16O, 40Ar13C, 40Ar12C1H on 53Cr; and 40Ar35Cl on 75As. The detection limits of the procedure were 0.008-0.019 ng As mL-1 and 0.084-0.087 ng Cr mL-1. The accuracy of the method has been validated by comparing the sum of the concentrations obtained for individual species with total concentration of the elements in NRCC SRM DORM-3 Fish Protein. The method has also been applied on three real samples, diabetic support formula tablets, diabetic support formula dietary fiber and Spirulina tablets , in which case the comparison has been made with total concentrations determined after complete dissolution of the samples. In this study, a microwave-assisted extraction method was used for the extraction of chromium and arsenic species from dietary supplemen samples. The extraction efficiency was better than 88% and the recoveries from spiked samples were in the range of 91–103%.